diff --git a/.gitignore b/.gitignore index 73e203a64..86bab2717 100644 --- a/.gitignore +++ b/.gitignore @@ -30,3 +30,4 @@ node_modules/ __pycache__/ *.pyc spec/**/generated +tmp/ \ No newline at end of file diff --git a/spec/API_specification/array_api/elementwise_functions.py b/spec/API_specification/array_api/elementwise_functions.py index 7acefaf52..43e5132d7 100644 --- a/spec/API_specification/array_api/elementwise_functions.py +++ b/spec/API_specification/array_api/elementwise_functions.py @@ -427,12 +427,20 @@ def cos(x: array, /) -> array: """ def cosh(x: array, /) -> array: - """ - Calculates an implementation-dependent approximation to the hyperbolic cosine, having domain ``[-infinity, +infinity]`` and codomain ``[-infinity, +infinity]``, for each element ``x_i`` in the input array ``x``. + r""" + Calculates an implementation-dependent approximation to the hyperbolic cosine for each element ``x_i`` in the input array ``x``. + + The mathematical definition of the hyperbolic cosine is + + .. math:: + \operatorname{cosh}(x) = \frac{e^x + e^{-x}}{2} **Special cases** - For floating-point operands, + .. note:: + For all operands, ``cosh(x)`` must equal ``cosh(-x)``. + + For real-valued floating-point operands, - If ``x_i`` is ``NaN``, the result is ``NaN``. - If ``x_i`` is ``+0``, the result is ``1``. @@ -440,15 +448,38 @@ def cosh(x: array, /) -> array: - If ``x_i`` is ``+infinity``, the result is ``+infinity``. - If ``x_i`` is ``-infinity``, the result is ``+infinity``. + For complex floating-point operands, let ``a = real(x_i)``, ``b = imag(x_i)``, and + + .. note:: + For complex floating-point operands, ``cosh(conj(x))`` must equal ``conj(cosh(x))``. + + - If ``a`` is ``+0`` and ``b`` is ``+0``, the result is ``1 + 0j``. + - If ``a`` is ``+0`` and ``b`` is ``+infinity``, the result is ``NaN + 0j`` (sign of the imaginary component is unspecified). + - If ``a`` is ``+0`` and ``b`` is ``NaN``, the result is ``NaN + 0j`` (sign of the imaginary component is unspecified). + - If ``a`` is a nonzero finite number and ``b`` is ``+infinity``, the result is ``NaN + NaN j``. + - If ``a`` is a nonzero finite number and ``b`` is ``NaN``, the result is ``NaN + NaN j``. + - If ``a`` is ``+infinity`` and ``b`` is ``+0``, the result is ``+infinity + 0j``. + - If ``a`` is ``+infinity`` and ``b`` is a nonzero finite number, the result is ``+infinity * cis(b)``. + - If ``a`` is ``+infinity`` and ``b`` is ``+infinity``, the result is ``+infinity + NaN j`` (sign of the real component is unspecified). + - If ``a`` is ``+infinity`` and ``b`` is ``NaN``, the result is ``+infinity + NaN j``. + - If ``a`` is ``NaN`` and ``b`` is either ``+0`` or ``-0``, the result is ``NaN + 0j`` (sign of the imaginary component is unspecified). + - If ``a`` is ``NaN`` and ``b`` is a nonzero finite number, the result is ``NaN + NaN j``. + - If ``a`` is ``NaN`` and ``b`` is ``NaN``, the result is ``NaN + NaN j``. + + where ``cis(v)`` is ``cos(v) + sin(v)*1j``. + + .. note:: + The hyperbolic cosine is an entire function in the complex plane and has no branch cuts. The function is periodic, with period :math:`2\pi j`, with respect to the imaginary component. + Parameters ---------- x: array - input array whose elements each represent a hyperbolic angle. Should have a real-valued floating-point data type. + input array whose elements each represent a hyperbolic angle. Should have a floating-point data type. Returns ------- out: array - an array containing the hyperbolic cosine of each element in ``x``. The returned array must have a real-valued floating-point data type determined by :ref:`type-promotion`. + an array containing the hyperbolic cosine of each element in ``x``. The returned array must have a floating-point data type determined by :ref:`type-promotion`. """ def divide(x1: array, x2: array, /) -> array:
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